1. Field of the invention
The present invention relates, in general, to a module for use in receiving teletext signals and, in particular, to a module for use in receiving teletext signals by being connected with a microcomputer or a videotex (still picture) system.
2. Description of the prior art
In the prior art, there is known a teletext adaptor composed of a data selector which separates the teletext data from input composite video signals, a data receiver which compares the teletext data with page address data to determine if there are errors in the received data, a CPU, a RAM used as an input/output buffer and a screen memory, a display controller, a keyboard interface and a keyboard. There is also known a videotex decoder comprising a bidirectional modem, an input/output port and a display controller. Thus, the videotex decoder comprises almost the same elements as those comprised by the teletext adaptor, that is, a CPU, a ROM, a RAM, a keyboard interface, a keyboard and a display controller. Accordingly, it is uneconomical to purchase a teletext adaptor in case one already has a videotex decoder or a personal computer.
One example of the prior art is found in Japanese patent publication No. 57-3268 issued on Jan. 20, 1982, in which a still picture receiving circuit equipped with the aforesaid adaptor element is described. The still picture receiving circuit described in the Japanese patent publication No. 57-3268 is characterized in that a vertical retrace interval of a television signal is used for insertion of a character broadcasting signal or a still picture signal and an interval during which the wanted multiinformation signal is received at the receiving side is displayed on the screen of the television set in order that the user may recognize the time during which the wanted information signal is displayed. However, the elements comprised in the said prior art are almost same as those comprised in the prior teletext adaptor. Another one of the prior art devices is disclosed in U.S. Pat. No. 3,757,225. The elements contained therein are almost same as those in the abovementioned art, namely, a bidirectional modem, an input/output port, a CPU, a ROM, a keyboard, a keyboard interface and a display controller. Hence, if the user purchases a teletext adaptor when he already has a videotex decoder or a personal computer, many of the components will be duplicated unnecessarily resulting in extra costs.
The present invention aims to provide a module for receiving teletext signals so that it may be used as a teletext adaptor for a personal computer.
Further, the present invention aims to provide a module for use in receiving teletext signals and for use by being connected with a videotex decoder so that expensive components need not be purchased twice.